"""Governance semver: the classifier labels amendments major / minor / patch.

Rules under test (docs/semver.md):
- any change to ``constitution/kernel/`` or ``constitution/invariants.yaml``
  is **major** (breaking change to the meta-rules);
- adding a userland module is **minor** (new capability, no meta-rule change);
- changing only parameter values inside an existing userland module is **patch**.
"""

from __future__ import annotations

import shutil

import pytest
import yaml

from tests.helpers import PROJECT_ROOT, classify, impact_of, tweak_first_numeric


def _tree(tmp_path, name):
    dest = tmp_path / name
    shutil.copytree(PROJECT_ROOT / "constitution", dest / "constitution")
    return dest


def _kernel_file(tree):
    files = sorted((tree / "constitution" / "kernel").glob("*.yaml"))
    assert files, "no kernel articles found"
    return files[0]


def _userland_file(tree):
    files = sorted((tree / "constitution" / "userland").glob("*.yaml"))
    assert files, "no userland modules found"
    return files[0]


def test_kernel_edit_is_major(tmp_path):
    base = _tree(tmp_path, "base")
    head = _tree(tmp_path, "head")
    article = _kernel_file(head)
    article.write_text(
        article.read_text(encoding="utf-8") + "\ntest_amendment_marker: kernel-change\n",
        encoding="utf-8",
    )
    assert impact_of(classify(base, head)) == "major"


def test_invariants_edit_is_major(tmp_path):
    base = _tree(tmp_path, "base")
    head = _tree(tmp_path, "head")
    invariants = head / "constitution" / "invariants.yaml"
    invariants.write_text(
        invariants.read_text(encoding="utf-8") + "\ntest_amendment_marker: invariant-change\n",
        encoding="utf-8",
    )
    assert impact_of(classify(base, head)) == "major"


def test_new_userland_module_is_minor(tmp_path):
    base = _tree(tmp_path, "base")
    head = _tree(tmp_path, "head")
    module = head / "constitution" / "userland" / "pet-policy.yaml"
    module.write_text(
        "id: pet-policy\n"
        "title: Household Pet Policy\n"
        "version: 0.1.0\n"
        "params:\n"
        "  max_pets: 3\n"
        "rules:\n"
        "  - id: pp-1\n"
        "    text: No citizen may keep more than max_pets pets.\n",
        encoding="utf-8",
    )
    assert impact_of(classify(base, head)) == "minor"


def test_userland_parameter_tweak_is_patch(tmp_path):
    base = _tree(tmp_path, "base")
    head = _tree(tmp_path, "head")
    module = _userland_file(head)
    doc = yaml.safe_load(module.read_text(encoding="utf-8"))
    new_doc, changed = tweak_first_numeric(doc)
    if not changed:
        pytest.skip("no numeric parameter found in the userland module to tweak")
    module.write_text(yaml.safe_dump(new_doc, sort_keys=False), encoding="utf-8")
    assert impact_of(classify(base, head)) == "patch"


def test_mixed_kernel_and_userland_is_major(tmp_path):
    base = _tree(tmp_path, "base")
    head = _tree(tmp_path, "head")
    article = _kernel_file(head)
    article.write_text(
        article.read_text(encoding="utf-8") + "\ntest_amendment_marker: kernel-change\n",
        encoding="utf-8",
    )
    module = head / "constitution" / "userland" / "extra-module.yaml"
    module.write_text("id: extra\ntitle: Extra module\n", encoding="utf-8")
    assert impact_of(classify(base, head)) == "major"


def test_no_change_is_not_major(tmp_path):
    base = _tree(tmp_path, "base")
    head = _tree(tmp_path, "head")
    result = classify(base, head)
    assert impact_of(result) in {"patch", "none", "noop", "no_change"}, (
        "an empty diff must never be classified as a breaking change"
    )